Maintaining healthy skin depends on the self-renewing capacity of stem cells deep within the skin's innermost layer. Cells originating from these stem cells proliferate and embark on a differentiation programme as they migrate towards the outer layers, which terminates as they near the skin's surface. A paper published online by Nature has discovered the switch mechanism responsible for imposing the molecular boundary between the proliferating basal cells and terminally differentiating outer skin cells.
MicroRNAs are small RNAs that do not encode proteins themselves, but which help to regulate the expression of other genes. Elaine Fuchs and her colleagues have identified a particular microRNA - called miR-203 - that stimulates the differentiation of epidermal stem cells. miR-203 is not expressed in epidermal stem cells, but it is made as cells commit to differentiate. It enforces differentiation by suppressing the production of p63, a protein that drives cell proliferation, thereby inducing the cells to stop dividing.
By this action, miR-203 ensures that the various layers of the skin retain their proper identities.
Elaine Fuchs (The Rockefeller University, New York, NY, USA)
Abstract available online.
(C) Nature press release.
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